Amplitude is referred to as:

Amplitude is a fundamental concept in sound and wave theory, representing the maximum extent of a vibration or oscillation, which directly correlates to the intensity or loudness of the sound produced. When amplitude increases, it results in a louder sound, while a decrease in amplitude leads to softer sounds. This relationship is crucial in understanding how we perceive sound; higher amplitude sounds are perceived as louder, while lower amplitude sounds are perceived as quieter.

In contrast, frequency refers to the number of vibrations or cycles per second and is associated with how high or low a sound is perceived, which is described as pitch. Speed or velocity relates to how fast a sound wave travels through a medium but does not describe the intensity of the sound. Waveform describes the shape of the sound wave itself, which can influence timbre but does not denote its loudness. Thus, understanding amplitude's relationship with intensity and loudness is key for anyone studying sound and hearing.